ML20217G019
| ML20217G019 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 10/15/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20217F997 | List: |
| References | |
| GL-90-05, NUDOCS 9910210157 | |
| Download: ML20217G019 (3) | |
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NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM ASME CODE REPAlR REQUIREMENTS FOR ASME CODE CLASS 3 PIPING
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FLORIDA POWER CORPORATION CRYSTAL RIVER UNIT 3 DOCKET NO. 50-302 1.0.l.NTRODUCTION By letter dated August 19,1999, Florida Power Corporation (the licensee) requested relief from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (the ASME Code),Section XI requirements regarding repair to a leak in a Class 3, moderate energy pipe at the Crystal River Unit 3 Nuclear Power Plant. The leak was detected in a 14-inch nominal pipe size nuclear service and decay heat sea water (RW) system pipe exiting the nuclear services closed cycle cooling heat exchangers. The RW system, which convoys sea water through the cooling heat exchangers, has a design temperature of 150 'F and pressure of 100 psi. The pipe is urethane-!ined carbon steel of nominal wall thickness of 0.375 inch.
The leak in the pipe was from a hole of 0.74 inch in diameter, located half way between the pipe flange and the pipe intersection. Currently, the leak is stopped by a temporary wooden plug. The licensee attributed the leak to a failure in the protective urethane lining bond, followed by corrosion attack on the inner surface of the carbon steel pipe. The ultraso'lic (UT) examir.ation at the leak locetion covered an area from the edge of the hole to about 4.0 inches from the hole. The thicknesses of the examined area range from 0.079 inch to 0.3 inch.
The licensee considered the on-line repair of the RW piping not practical because the flay / is located in a section of Class 3 piping that cannot be isolated for completing a Code repair within the time period permitted by the limiting condition for operation for the affected system as specified in the plant technical specifications. Based upon the above, the licensee submitted a relief request in accordance with the provisions of Generic Letter (GL) 90-05,
" Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1,2, and 3 Piping." The licensee requested relief until a Code repair can be performed during the next refueling outage, R11, scheduled to begin October 1,1999.
2.0 DISCUSSION AND EVALUATION Title 10 Code of Federal Reaulations (10 CFR), Section 50.55a(g), requirec nuclear power facility piping and components to meet the applicable requirements of Section XI of the Code.
This section of the Code specifies Code-accept.:ble repair methods for flaws that exceed Code acceptance limits in piping that is inservice. A Code repair is required to restore the stfJClural 9910210157 991015 PDR ADOCK 0 302 ENCLOSURE
. integrity of flamd Code piping, independent of the operational mode of the plant when the i
flaw is detected.- Those repairs not in compliance with Section XI of the Code are non-Code repairs.
in some circumstances the required Code repair may be impractical unless the facility is shut down. In such cases, the U.S. Nuclear Regulatory Commission (NRC) may evaluate determinations of impra %cality and may grant relief and impose altemative requirements pursuant to 10 CFR 50.55a(g)(6)(i). GL 90-05, " Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1,2, and 3 Piping"(dated June 15,1990), provides guidance to the staff for evaluating relief requests submitted by licensees for temporary non-Code repairs to Code class 3 piping.
On November 7,1991, the NRC issued GL 91-18, "Information to Ucensees Regarding Two NRC Inspection Manual Sections on Resolution of Degraded and Nonconforming Conditions and on Operability." This GL and NRC Inspection Manual Part 9900 provide detailed discussions of specific operability deterrninations, one of which is operationalleakage. In this regard, Section 6.15 of Part 9900 states the following:
"Upon discovery of leakage f rom a Cicas 1,2, or 3 component pressure wall (i.e., pipe wall, valve body, pum casing, etc.) the licensee should declare the component inoperable. The oniy exception is Class 3 moderate energy piping as discussed in Generic Letter 90-05. For Class 3 moderate energy piping, the licensee may treat the system containing the through-wall flaw (s), evaluated and found to meet the acceptance criteria in Generic Letter 90-05, as operable until relief is obtained from the NRC."
The licensee has evaluated the flaw in accordance with GL 90-05. The licensee has used the "through-wall flaw" approach for the pin hole area of the RW pipe. For the general cross section of the degraded pipe, the licensee evaluated the structuralintegrity in accordance with American National Standards institute (ANSI) B31.1 (1967) Power Piping Code. The licensee concluded that the structural integrity is adequate for continued operation of the Unit for about a month and proposed to install a wooden plug to stop or reduce the leakage from the RW pipe pin hole for housekeeping purposes.
The staff reviewed the evaluation and confirmed that the through-wall flaw evaluation is in accordance with GL 90-05 and the integrity evaluation of the general cross section of the l
degraded pipe is in accordance with the ANSI Code, which is consistent with the current licensing bases. It should be noted that in determining the minimum pipe wall thicknesses due to design, upset, and faulted conditions, the ANSI Code is more conservative than the current ASME Code. The maximum thickness of the examined area around the hoie is 0.3 inch, less t
than the nominal pipe wall thickness cf 0.375 inch, indicating the degradation of the pipe is j
. beyond the examined area. Since the licensee conservatively assumed that the nominal pipe wall thickness is 0.2 inch in its calculations, there it no need to expand the UT to determine the full degradation of the pipe around the hole. Further, the issues of flooding (assuming that the plug fails), water spraying on other equipment, and loss of flow were analyzed and found to be manageable to the operation of the RW system. The licensee has also performed an augmented inspection using UT. This inspection did not find any additional locations with degradetion below Code requirements for wall thickness.
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CONCLUSION The staff has reviewed the licensee's request for relief and finds that the licensee has followed the analytical methods provided in GL 90-05. Furthermore, the staff finds that performing a Code. repair on the leakirig sea water pipe while the unit is operating is impractical. The staff
. concludes that the granting of relief where Code requirements are impractical and imposing alternative requirements is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest, given due consideration to the burden upon the licensee and facility that could result if the Code requirements were imposed on the facility.- Pursuant to 10 CFR 50.55a(g)(6)(i) and consistent with the guidance in GL 90-05, relief is granted until the next refueling outage, scheduled to start on October 1, 1999. The temporary non-Code repair must then be replaced with a Code repair.
Principal Contributor: S. Sheng, NRR Date: October 15,.1999 l
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